On-Demand, Tankless Water Heaters

by Kim Kinrade

With energy costs soaring home owners are looking to curb their heating costs and seal their homes from the elements. New advances in windows, doors and insulation have aided in this quest for lower fuel costs as well as advances in furnace technology. One of the biggest energy drains in a home is heating water.

Water Storage Heaters

An average home is supplied by an electric or fuel-burning water heater, many of which maintain a capacity of 40-60 gallons. These are insulated, cylindrical units located in a garage or basement which switch on to maintain an even temperature so that hot water can be available at any time of the day. If the water is used consistently then the costs go up. However, there is still a cost to keep the water consistently hot for the next use.

A regular water heater is much like a home furnace in that it is usually centrally-located so that it can supply the needs for the entire home. Cold water flows into the bottom as the hot water is being used. Because water forms layers at different temperatures the hot water stays at the surface and flows out from there while the heat element goes to work on the cold water that has just arrived.

Electric water heaters are rated for efficiency by what is called “stand-by loss,� which is measure of how much power it takes to maintain the temperature of the tank whether it is being used or not. This means that a large water heater which does not get used very much is actually costing more per shower than if the tank were used consistently. This is why many people are switching to an on-demand system which means that the water is heated only when it is needed.

On-Demand Water Heating

On-demand water heaters, also called tankless water heaters, are an instantaneous, in-line water heating system which heat the incoming water flowing through the device with a coil heated by either electricity or gas. Unlike the tank model they do not retain or store any hot water but rely on a series of coiled, metal tubing which is absorbs the heat much like tubes in a boiler.

Tankless units are are not much bigger than an ordinary power panel. The process starts when you turn on the hot water faucet. A flow sensor alerts a processor which switches on the heating unit. If the unit is heated by gas a burner comes on and flash-heats the water contained in a tight coil of copper pipe. Water that flows through theses heated pipes is consistently heated and when the tap is turned off the flow sensor signals the processor and the burner shuts off. The water heated is the water being used, no more and no less. If the water is heated electrically then the coils are heated by electricity.

The operation of a tankless system has to be calibrated by a plumbing and heating professional to ensure that the unit can handle the biggest load that household requires. For example, the smaller tanks can usually produce a gallon a minute or one shower. So if you have a family of five you would need a high-capacity nit because there may be two people showering at the same time and hot waters may be on as well. For a couple in a small home a small capacity one will do.

Satellite Units

Another great feature with tankless water heaters is that small ones can be placed where they are needed. In other words if you have a two bathrooms and a laundry room you can place one unit by each one. This cuts down on the time it takes for the water to reach the faucet and thereby cutting down on the cost of heating. Some households have 3 units.

In addition, if you are using natural gas, then there has to be allowances made for venting. For safety purposes these units have to be placed on an outside wall for exhaust and the exhaust pipe must be a measured distance from the windows. In addition, it must be mounted on cement board or some other non-combustible material. So, this is not a do-it-yourself project but one which involves skill and experience..

A Renovator's Dream

If you are adding on a section to your home which includes a kitchen or bathroom, running hot water pipe from the water heater may be quite a distance. Having an on-demand, tankless heater by the bathroom shortens the distance that the hot water has to travel, saving money in the long run.